Authors:

K. Ninios(Department of Physics, University of Florida)

H.B. Chan(Department of Physics, University of Florida)

We measure the spectrum of fluctuations of a nonlinear underdamped
micromechanical oscillator, whose nonlinearity can be
electrostatically
tuned. In the linear regime where the eigenfrequency is
independent of the
energy of the oscillator, the spectral peaks are
well-characterized by a
lorentzian lineshape, the width of which is determined by the
relaxation
rate. In the presence of cubic nonlinearity in the restoring
force, the
eigenfrequency depends monotonically on the energy. As a result,
the energy
straggling due to fluctuations gives rise to frequency
straggling. For
sufficiently large fluctuation intensity the frequency straggling
exceeds
the frequency uncertainty due to relaxation and broadening of the
spectral
peaks with fluctuation intensity is observed. We also measure the
fluctuation spectrum when the dependence of the eigenfrequency of
the
oscillator on energy is not monotonic due to higher order
nonlinearities.
Our measurements indicate that for a certain range of parameters,
it is
possible for the width of the spectral peak to decrease as the
fluctuation
intensity increases.

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2010.MAR.V14.11